This invention relates generally to gas burners, and, more particularly, to methods and apparatus for gas burner assemblies including inner and outer burners.
For gas burners that are used as surface heating units in cooking appliances such as ranges and cooktops, having a high turndown ratio, which is a ratio of maximum output to minimum output, is desirable. For a given burner, the maximum output typically signifies the “power” or “speed” of the burner and the minimum output is related to the simmer capability of a burner. The maximum output is limited by system gas flow handling capabilities and safety considerations. The minimum output is limited by the ability of the burner to maintain a stable flame under transient pressure fluctuation conditions caused, for example, by air currents in the room, or sudden opening or closing of nearby cabinet doors or the oven door.
A vast majority of gas burners used in cooking applications are partially pre-mixed burners using both primary-air and secondary-air. Based on whether the primary-air is drawn from above the cooktop or below the cooktop, these burners are termed either top-breathers or bottom-breathers respectively. In bottom-breather burners, also referred to as sealed burners, there are no gaps around the burner to allow spills or air to get inside the cooktop. However, the sealed burners are sensitive to pressure fluctuations under the cooktop.
At least some known gas burner assemblies include an inner gas burner and an outer gas burner for collectively producing a plurality of rings of flame to heat a utensil supported thereon. Such gas burners are generally secured on a cooktop surface by screws, and it is difficult to clean the cooktop surface around and between the burners. The inner burner is surrounded by the outer burner, and secondary-air cannot flow through the outer flame ring to enter the inner flame ring, such that the maximum energy output of the inner burner is undesirably limited unless a gap is provided either through or under the other burner. This further increases the difficulty of cleaning the cooktop.